.box {
    position: relative;
    width: 500px;
    height: 500px;
}

.btn {
    position: absolute;
    left: 520px;
    width: 100px;
    height: 40px;
    outline: none;
    border: none;
    border-radius: 3px;
    background-color: #5FB878;
    cursor: pointer
}

.start {
    top: 8px;
}

.back {
    top: 58px;
}

.step {
    top: 108px;
}

.messageBox {
    display: none;
    position: absolute;
    top: 190px;
    left: 150px;
    width: 200px;
    height: 120px;
    background-color: #ddd;
    border-radius: 3px;
}

.prompt {
    display: flex;
    justify-content: space-between;
    padding: 0 10px;
    padding-left: 10px;
    height: 30px;
    line-height: 30px;
    background-color: #ccc;
}

.close {
    cursor: default;
    font-size: 24px;
}

.close:hover {
    color: #f00;
}

.text {
    height: 60px;
    font-size: 22px;
    padding-left: 40px;
    line-height: 60px;
}

.confirm {
    display: block;
    width: 56px;
    height: 26px;
    margin-left: 138px;
}

.piece {
    position: absolute;
    width: 40px;
    height: 40px;
    cursor: default;
    border-radius: 50px;
    -webkit-border-radius: 50px;
    -moz-border-radius: 50px;
    -ms-border-radius: 50px;
    -o-border-radius: 50px;
}